Wireless reservoir production control

ABSTRACT

A reservoir production control system includes a plurality of wells for producing a reservoir linked to a central computer over a downhole communication network and a surface communication network. Both the downhole and the surface communication networks are wireless communications paths for transmitting downhole data and surface data to the central computer. Both networks include a series of interconnected tubing or pipe that allows transmission of data over electrically isolated portions of the pipe and tubing. After integrating and analyzing all relevant data and comparing the data with a reservoir model, the central computer initiates changes in a plurality of downhole control devices associated with the wells, thereby optimizing the production of the reservoir.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates in general to reservoiroptimization and more specifically to petroleum wells having downholeindependently addressable wireless measurement and control devices thatcommunicate with surface power and telemetry devices such thatproduction from individual zones within individual wells may becoordinated to optimize overall reservoir production.

[0003] 2. Description of Related Art

[0004] Oil and gas reservoirs are extensive three-dimensional subsurfacegeological structures whose fluid contents are produced through arraysof wells which withdraw fluids from the reservoir only at points wherethe wells pass through the producing zones. As fluids are withdrawn atthe wells, pressure differentials develop within the reservoir which inturn create displacement of fluids from more distant reservoir regionstowards the producing wells. To assist in sweeping desired fluidstowards the producing wells, it is common practice in some fields topump water or other fluids into wells which are designated injectionwells.

[0005] To assist in comprehending the changing condition of thereservoir and thus manage production from individual wells to optimizerecovery from the field overall, it is common practice to develop areservoir model which reflects the relevant characteristics of theformation's fixed matrix such as porosity and permeability, and thecomposition, pressure, and temperature of the fluids contained withinthat matrix. The parameters of both the matrix and the fluids areexpected to change as fluids are withdrawn from the producing wells andinjection fluids are introduced at the injection wells. Since thegeological formations of the reservoir are generally heterogeneous, thestarting values of the matrix and fluid parameters are spatialvariables, and as production evolves the changes in these parameters arealso spatially variable in addition to being time dependent.

[0006] The data used to generate a reservoir model come from manysources. Three-dimensional seismic surveys provide stratigraphy andfaulting, and wireline logging, existing well production historiesprovide, and to a lesser extent seismic surveys, provide data onformation fluids.

[0007] The starting values of the reservoir model parameters adjacent toeach well can be measured relatively easily using wireline logging toolsbefore each well is cased, but once production has commenced thepresence of the well casing prevents many of the measurements which canbe made in an open hole. Even measurements which could be made throughthe casing are usually not performed in existing practice since doing sowould require either removing the production hardware and tubing fromthe well and running cased hole wireline logs, or the use of permanentdownhole sensors connected to surface equipment by cables which extendthe full depth of the well. These cables are expensive, are not entirelyreliable, often introduce operational problems, and their installationat the time of completion complicates that process. The same issue ofrequiring cables to operate downhole control equipment such as valvesalso discourages the use of such devices. When downhole control devicesare absolutely required, the provision of permanently installed cablescan be avoided by using slickline tools, but cost prevents these fromaltering the settings of downhole devices at frequent intervals.

[0008] All references cited herein are incorporated by reference to themaximum extent allowable by law. To the extent a reference may not befully incorporated herein, it is incorporated by reference forbackground purposes and indicative of the knowledge of one of ordinaryskill in the art.

BRIEF SUMMARY OF THE INVENTION

[0009] The difficulties inherent with restricted measurement and controlare largely resolved by methods in accordance with the presentinvention. Wireless power and communications as described in the RelatedApplications enable the wells to provide real-time measurement ofdownhole conditions to update the reservoir model, and based onpredictions made from the model, the well production is controlled tooptimize field performance. The objective function for productionoptimization may be altered over time as product market conditionsshift, production costs vary, or physical plant capabilities arechanged.

[0010] The invention and development of wireless communication andelectrical power transmission and control by means of pipes and tubingintroduces the opportunity for widespread collection of oil field data,both (1) at the surface, through the network of facilities piping andinjection and production distribution lines, and (2) in the subsurface,through well casing and tubing. The amounts and types of data that couldbe collected and the degree of control in remote parts of the unitswould provide a major advance in management of single wells, wholefields, or even company-wide assets.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 schematically illustrates a reservoir production controlsystem according to the present invention being implemented on acompany-wide basis to optimize the production of a plurality ofreservoirs.

[0012]FIG. 2 depicts secondary production operations in a multi-layerreservoir being produced by two wells.

[0013]FIG. 3 illustrates primary production operations in a multi-layerreservoir by a production well, the production well experiencing wateror gas breakthrough in one layer of the reservoir before another layeris oil depleted.

[0014]FIG. 4 is a flow diagram illustrating the measurement, modeling,and control actions method for closed-loop control of an individual wellor a field.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] Referring to FIG. 1 in the drawings, a reservoir productioncontrol system 11 according to the present invention is illustrated.Reservoir production control system 11 is used to optimize theproduction of one or more reservoirs. A reservoir 13 includes aplurality of wells 15, 17, 19, 21 completed in the subsurface forproducing oil and gas reserves from reservoir 13. The exact number andtype of wells present in a particular reservoir could vary significantlyfrom reservoir to reservoir. In FIG. 1, well 15 is an injection well,well 17 is a conventional production well, well 19 is a multi-lateralproduction well, and well 21 is a data observation well. Each wellincludes a borehole that begins at a surface of the well and continuesinto a production zone within the reservoir. Preferably, the wellsinclude casing that is cemented in the borehole during completion of thewell. A tubing string or production tubing 29 is located in the boreholeof each well.

[0016] Wireless data receptors or downhole data pods 31 are distributedin the boreholes of the wells. Downhole data pods 31 send and receivedata along a downhole communication network 33. Preferably, the downholecommunication network allows transmission of data signals along anelectrically isolated portion of the tubing string. In most cases, theelectrically isolated portion of the tubing string is created betweentwo ferromagnetic chokes placed on the tubing string. The transmissionof data using such electrically isolated sections of pipe or tubing isdescribed more fully in U.S. Pat. App. No. 60/177,999, entitled“Toroidal Choke Inductor for Wireless Communication and Control,” filedJan. 24, 2000, and U.S. Pat. App. No. 60/178,000, entitled“Ferromagnetic Choke in Wellhead,” filed Jan. 24, 2000, which are bothhereby incorporated by reference. Pods 31 may also be equipped tocollect data about downhole physical characteristics of the well,including pressure, temperature, acoustic noise, seismic signals,resistivity, fluid turbidity, infrared response, flow rate in the pipe,vibration, or other measurements useful for monitoring the well. Thisdata collection would be accomplished in the manner described in U.S.Pat. App. No. 60/177,998, entitled “Petroleum Well Having DownholeSensors, Communication, and Power,” filed Jan. 24 2000, which is herebyincorporated by reference. Collected data would be transmitted to thesurface of the well over the downhole communication network 33 using themethods described in U.S. Pat. App. No. 60/177,999, entitled “ToroidalChoke Inductor for Wireless Communication and Control,” filed Jan. 24,2000, and U.S. Pat. App. No. 60/178,000, entitled “Ferromagnetic Chokein Wellhead,” filed Jan. 24, 2000. In some cases pod 31 would beequipped to operate accompanying downhole control devices 35, whichcould include a submersible pump or a controllable gas-lift valve formodifying the flow rate of oil within the production tubing 29. Thedownhole control device 35 could also include a chemical injector forinjecting treatment chemicals such as corrosion inhibitors, scaleinhibitor, foaming agents and paraffin solvents. The operation ofdownhole valves using the power transmission and communicationtechniques described above is more fully described in U.S. Pat. App. No.60/178,001, entitled “Controllable Gas-Lift Well and Valve,” filed Jan.24, 2000, which is hereby incorporated by reference. Detection offailures of downhole equipment, such as gas-lift valve leakage, electricsubmersible pump vibration, and rod pump noise, would allow earlyremedial efforts that would improve productivity of the wells.

[0017] In addition to placement of wireless devices in the subsurfaceportions of the wells, a plurality of surface data pods 37 may be placedin a surface communication network 38 of interconnected pipes 39. Theinterconnected pipes 39 are common in oil field operations and aregenerally used to fluidly connect the wells to tanks and separators 41.Each of the interconnected pipes is also a potential data transmissionpath when a section of the pipes can be electrically isolated asdescribed in U.S. Pat. App. No. 60/177,999, entitled “Toroidal ChokeInductor for Wireless Communication and Control,” filed Jan. 24, 2000,and U.S. Pat. App. No. 60/178,000, entitled “Ferromagnetic Choke inWellhead,” filed Jan. 24, 2000. Preferably, the electrically isolatedportions of the interconnected pipes are located between ferromagneticchokes placed on the pipes. The wireless devices at the surface wouldinteract with the subsurface devices to optimize well production in viewof any operational constraints at the surface. These constraints mightbe (1) available gas for gas lift, (2) supply of water or other fluidsfor flooding projects, (3) upsets in production facilities such asoil/water separation, (4) emulsion control, and (5) other commonoccurrences encountered in manual operations.

[0018] Control of all of the operations described above resides in acentral data collection computer 51, which will have a reservoir modelwith which to compare the actual behavior of the reservoir beingmonitored by downhole data pods 31. Reservoir conditions that changewith time are often unattainable after wells have been completed andpipe cemented in place. With permanent pressure monitors available fortimely pressure transient analyses, the progress of depletion of areservoir can be closely monitored. Deviations from expected behavior,can be analyzed and in some cases, such as poor profile control, may becorrected by the downhole control devices 35, or by well workovers.

[0019] Permanently installed resistivity monitors in producing wellswould be effective in observing the effects of poor injection profiles.Referring to FIG. 2 in the drawings, a multi-layer reservoir 61 withproduction well 63 and an injection well 65 is illustrated duringflooding operations of secondary production. Downhole sensing andcontrol devices are used to regulate injection into individual layers,in order to prevent early breakthrough of injected fluids and tominimize wasteful cycling of injectants during sweepout of the otherlayers. This is accomplished by monitoring and controlling flow rates ata number of locations along the injection interval. Alternatively,layers that flood out prematurely can be detected by salinity devices orother detectors spaced along the interval in production well 63.

[0020] Referring to FIG. 3 in the drawings, a multi-layer reservoir 71being produced by a production well 73 is illustrated during primaryproduction. Well 73 is experiencing water or gas breakthrough in onelayer of the reservoir before another layer of the reservoir is depletedof oil. By placing downhole equipment and downhole control devices inthe layers experiencing water or gas breakthrough, production from theselayers can be excluded, thereby permitting continued oil production fromlayers that are relatively free of gas or water.

[0021] The values of downhole data are compared with the reservoir modelprediction to determine if the reservoir is operating as expected. Whenthe reservoir operating parameters diverge from expected behavior, newwells may be required, or wells may need to be shut in or abandoned;however, many corrective operations are potentially attainable with theproposed downhole control devices.

[0022]FIG. 4 illustrates a measurement and control sequence appropriateto such corrective actions. As illustrated in FIG. 4, such a sequence iscyclic:

[0023] Measurements from downhole and surface sensors are collected andpassed to the model;

[0024] The model may be updated from an external data source, forinstance to alter desired production rate, and the measurements arecompared to the model;

[0025] Based on the results of the comparison, decisions are taken onany action which may be required, and the model parameters are updated;

[0026] Any decisions for action are translated into commands which aretransmitted to downhole actuators, and the cycle returns to themeasurement step.

[0027] Reservoir management is not limited to optimization of a singlefield. Referring again to FIG. 1, a second central computer 77 and athird central computer 79 are associated with a second reservoir and athird reservoir, respectively. Similar to central computer 51, thesecond and third central computers 77, 79 monitor downhole data andsurface data over individual downhole communication networks (not shown)and individual surface communication networks (not shown). The datacollected by second central computer 77 and third central computer 79are integrated with that data collected by central computer 51 over aremote communication network 91. The integration of data among thecentral computers 51, 77, 79 could include data for all of the fieldsoperated by a particular company. This data can then be integrated andanalyzed in conjunction with economic data 93 and world-wide economictrends, such as oil prices and supplies, national production controls,pipeline and tanker capacities, and location storage limitations. Theoverall effect of having large amounts of information and control in acentral location by efficient wireless devices would allow effectiveoptimization of production from all of a company's assets.

We claim:
 1. A reservoir production control system comprising: aplurality of wells disposed on a reservoir, each well having a boreholeand at least one piping structure located within the borehole; a centralcomputer for collecting downhole data from one or more wells; a downholecommunication network associated with one or more wells, the downholecommunication network being capable of conveying electricalcommunication signals along the tubing string piping structure of thewell with electrically isolated portions of the piping structure definedby electrical chokes; a surface communication network for communicatinginformation between the downhole communication network and the centralcomputer; and whereby the central computer receives downhole data viathe downhole communication network and the surface communicationnetwork.
 2. The production control system according to claim 1, wherein:the downhole data collected from the wells is compared to a reservoirmodel; and wherein a selected well of the plurality of wells is adjustedto optimize production of the reservoir.
 3. The production controlsystem according to claim 1, wherein the surface communication networkincludes wiring that electrically connects the downhole communicationnetwork to the central computer.
 4. The production control systemaccording to claim 1, wherein the surface communication networkincludes: a plurality of interconnected pipes located between thedownhole communication network and the central computer; and whereincommunication occurs between the downhole communication network and thecentral computer by passing communication signals along electricallyisolated sections of the interconnected pipes.
 5. The production controlsystem according to claim 4, wherein the electrically isolated sectionsof interconnected pipe are created by placing ferromagnetic chokes atselected locations along the pipe, the ferromagnetic chokescircumferentially surrounding the pipe and impeding current flow throughthe pipe.
 6. The production control system according to claim 1, whereincommunication and power transmission within the downhole communicationnetwork occurs along an electrically isolated section of the tubingstring.
 7. The production control system according to claim 6, whereinthe electrically isolated section of the tubing string is locatedbetween a first and a second ferromagnetic choke disposedcircumferentially around the tubing string, both ferromagnetic chokesimpeding current flow along the tubing string.
 8. The production controlsystem according to claim 1, further comprising: a second centralcomputer for collecting downhole data from a second reservoir; whereinthe second central computer is electrically connected to the firstcentral computer via a remote communication network; and wherein thedownhole data collected by the first and second central computers isanalyzed and used to collectively optimize the production of the firstand second reservoir.
 9. A reservoir production control systemcomprising a plurality of wells for producing a reservoir, each wellhaving a borehole extending from the surface, and at least one pipingstructure located within the borehole; at least one downhole data podlocated within the borehole of one of the wells for monitoring downholedata about downhole physical characteristics of the well; at least onesurface data pod for monitoring surface data; a central computer forcollecting the surface data from the surface data pod and the downholedata from the downhole data pod; a downhole communication network fortransmitting alternating current electrical power and communicationsignals along an electrically isolated portion of the piping structureof the one or more wells from the downhole data pod to the surface ofthe one or more wells; a surface communication network electricallyconnected between the surface of the well and the central computer;wherein the surface communication network includes a plurality ofinterconnected pipes having electrically isolated portions forcommunicating information between the surface of the well and thecentral computer, and wherein the downhole data and the surface data isanalyzed by the central computer to optimize production of thereservoir.
 10. The production control system according to claim 9,further comprising: a second central computer for collecting downholedata and surface data associated with a second reservoir, the secondcomputer receiving the data over a second surface communication network;and wherein the second central computer is electrically connected to thefirst central computer.
 11. The production control system according toclaim 9, further comprising: a second central computer for collectingdownhole data and surface data associated with a second reservoir, thesecond computer receiving the data over a second surface communicationnetwork; wherein the second central computer is electrically connectedto the first central computer over a remote communication network; andwherein the downhole and surface data collected by the second computerand the downhole and surface data collected by the first centralcomputer are analyzed to optimize the production of both the firstreservoir and the second reservoir.
 12. The production control systemaccording to claim 11, wherein economic data is also provided to one ofthe central computers, the economic data being considered in conjunctionwith the surface data and the downhole data from both reservoirs tocollectively optimize the production of the first reservoir and thesecond reservoir.
 13. The production control system according to claim12, wherein the economic data is information on petroleum prices. 14.The production control system according to claim 12, wherein theeconomic data is information on petroleum supplies.
 15. The productioncontrol system according to claim 12, wherein the economic data isinformation on national production controls.
 16. The production controlsystem according to claim 12, wherein the economic data is informationon pipeline capacities.
 17. The production control system according toclaim 12, wherein the economic data is information on tanker capacities18.
 18. The production control system according to claim 12, wherein theeconomic data is information on location storage limitations.
 19. Theproduction control system according to claim 9, further comprising atleast one downhole control device electrically connected to the downholecommunication network, the downhole control device receivinginstructions from the central computer to assist in optimizing theproduction of the reservoir.
 20. The production control system accordingto claim 19, wherein the downhole control device is a controllablegas-lift valve disposed along the tubing sting of the well.
 21. Theproduction control system according to claim 19, wherein the downholecontrol device is an electric submersible pump.
 22. The productioncontrol system according to claim 19, wherein the downhole controldevice is a chemical treatment injector.
 23. The production controlsystem according to claim 19, wherein the downhole control device is aninflow control device.
 24. The production control system according toclaim 9, wherein at least one of the wells is a conventional productionwell.
 25. The production control system according to claim 9, wherein atleast one of the wells is an injection well.
 26. The production controlsystem according to claim 9, wherein at least one of the wells is amulti-lateral production well.
 27. The production control systemaccording to claim 9, wherein at least one of the wells is a dataobservation well.
 28. A method for controlling the production of areservoir having a plurality of wells for producing the reservoir, eachwell having a borehole extending from the surface, and a tubing stringinserted in the borehole, the method comprising the steps of: (a)communicating downhole data from a downhole pod in at least one of thewells to the surface along a downhole communication network utilizing anelectrically isolated portion of the tubing string; (b) providing acentral computer for collecting the downhole data from one or morewells; (c) communicating the downhole data from the surface of the wellto the central computer along a surface communication network; and (d)analyzing the downhole data and communicating instructions from thecentral computer to at least one of the wells to change selectedoperating parameters of the well.
 29. The method according to claim 28further comprising the step of comparing the downhole data collected bythe central computer to a reservoir model.